The molecular properties of aldohexoses and ketohexoses are usually studied in the context of their cyclic, furanose or pyranose structures which is due to the abundance of related tautomeric forms in aqueous solution. We studied the conformational features of a complete series of d-aldohexoses (d-allose, d-altrose, d-glucose, d-mannose, d-gulose, d-idose, d-galactose and d-talose) and d-ketohexoses (d-psicose, d-fructose, d-sorbose and d-tagatose) as well as of l-psicose by using microsecond-timescale molecular dynamics in explicit water and DMSO with the use of enhanced sampling methods. In each of the studied cases the preferred conformation corresponded to an extended chain structure; the less populated conformers included the quasi-cyclic structures, close to furanose rings and common for both aldo- and ketohexoses. The orientational preferences of the aldehyde or ketone groups are correlated with the relative populations of anomers characteristic of cyclic aldo- and ketohexoses, respectively, thus indicating that basic features of anomeric equilibria are preserved even if hexose molecules are not in their cyclic forms.

2.Construction of a Food Grade Recombinant Bacillus subtilis Based on Replicative Plasmids with an Auxotrophic Marker for Biotransformation of d-Fructose to d-Allulose.

A food grade recombinant Bacillus subtilis that produces d-psicose 3-epimerase (DPEase; EC 5.1.3.30) was constructed by transforming a replicative multicopy plasmid with a d-alanine racemase gene marker into B. subtilis 1A751 with the d-alanine racemase gene knocked out. The DPEase was expressed in B. subtilis without antibiotic resistance genes and without adding antibiotics during fermentation. Whole cells of the food grade recombinant B. subtilis were used to biotransform d-fructose to d-allulose. The two tandem promoters, including the HpaII and P43 promoters, increased expression levels compared to the use of one promoter, HpaII. For large-scale d-allulose production, the optimal enzyme dose was 40 enzyme activity units of dry cells per gram of d-fructose, which produced a 28.5% turnover yield in 60 min. The recombinant plasmid exhibited stability over 100 generations. This food grade recombinant B. subtilis may be used for large-scale d-allulose production in the food industry.

3.Efficient synthesis and activity of beneficial intestinal flora of two lactulose-derived oligosaccharides.

Lactulose is considered as a prebiotic because it promotes the intestinal proliferation of Lactobacillus acidophilus which is added to various milk products. Moreover, lactulose is used in pharmaceuticals as a gentle laxative and to treat hyperammonemia. This study was aimed at the total synthesis of two Lactulose-derived oligosaccharides: one is 3-O-β-d-galactopyranosyl-d-fructose, d-fructose and β-d-galactose bounded together with β-1,3-glycosidic bound, the other is 1-O-β-d-galactopyranosyl-d-fructose, d-fructose and β-d-galactose bounded together with β-1,1-glycosidic bound, which were accomplished in seven steps from d-fructose and β-d-galactose and every step of yield above 75%. This synthetic route provided a practical and effective synthetic strategy for galactooligosaccharides, starting from commercially available monosaccharides. Then we evaluated on their prebiotic properties in the search for potential agents of regulating and improving the intestinal flora of human.

A number of findings suggest that zero-calorie D-psicose has beneficial effects on obesity-related metabolic disturbances. However, it is unclear whether D-psicose can normalize the metabolic status of diet-induced obesity without having an impact on the energy density. We investigated whether 5% D-psicose supplementation in a high fat diet(HFD) could normalize body fat in a diet-induced obesity animal model under isocaloric pair-fed conditions. Mice were fed a HFD with or without various sugar substitutes(D-glucose, D-fructose, erytritol or D-psicose, n = 10 per group) for 16 weeks. Body weight and fat-pad mass in the D-psicose group were dramatically lowered to that of the normal group with a simultaneous decrease in plasma leptin and resistin concentrations. D-psicose lowered plasma and hepatic lipids while elevating fecal lipids with a decrease in mRNA expression of CD36, ApoB48, FATP4, in the small intestine. In the liver, activities of both fatty acid synthase and β-oxidation were down-regulated by D-psicose to that of the normal group level; however, in WAT, fatty acid synthase was decreased while β-oxidation activity was enhanced.